Medicinal oil and method of preparation



Patented Oct. 3, 1933 MEDICINAL OIL AND METHOD OF PREPARATION Seymour W.Ferris, Aldan, Pa., assignor to The Atlantic Refining Company,Philadelphia, Pa., a corporation of Pennsylvania No Drawing. ApplicationAugust 14,

Serial No. 1933 18 Claims.

The present invention relates to the art of refining mineral oils, withparticular reference to a method of producing white mineral oils, such,for example, as those used for medicinal purposes.

The product resulting from such method, which is characterized bycertain particularly desirable properties, also comes within the purviewof this.

invention.

In accordance with prior practice, white mineral oils are prepared bysubjecting a carefully selected fraction of a crude petroleum totreatment with large quantities of acid, usually fuming sulphuric acid,the quantity of acid required for the preparation of the most highlyrefined medicinal oils being of the order of 75% or more by weight ofthe oil treated. By such processes the yield of final product in generaldoes not exceed 50% of the amount of the fraction used in itspreparation, the'remaining 50% comprising acid sludge which is of littlevalue. Furthermore, the product or products obtained have less desirablephysical characteristics than do products obtained in accordance withthis invention. A comparison of the characteristics of my product withwhite oils heretofore produced will be brought out in another part ofthis specification.

White mineral oils such as those used for medicinal purposes aresubstantially water-white viscous products which, in accordance with theprior practice, have been obtained by subjecting a carefully selectedfraction of a crude petroleum, as for example, a fraction fromPennsylvania crude, to a drastic acid treatment as aforesaid. Thistreatment, due to the large quantities of strong acid used, results inthe destruction of the less stable constituents contained in the oil,which probably accounts for the high oil loss incident to suchtreatment. This loss is referred to as an oil loss since the portion ofthe oil which reacts with the acid to form a sludge is only partiallyrecoverable, and even when recovered it is usable only as a low gradefuel oil which has a very low market value.

Furthermore, processes in accordance with the produce a white mineraloil from a petroleum' fraction having a viscosity greater than 450seconds Saybolt Universal at 100 F., as far as I am aware. I

' prior practice whereby white mineral oils are 1928, Renewed February16,

An object of my invention is the preparation of white mineral oils,particularly oils to be used for medicinal purposes, which haveproperties materially and distinctly different from the properties ofsuch oils as are now on the market. For example,.white mineral oilswhich have a viscosity as high as 500 seconds Saybolt Universal at 100F., have not heretofore been known, whereas, such oils may be preparedin accordance with my invention.

This invention contemplates a process more efficient than processes forthe manufacture of white mineral oils which have been known heretofore.

In accordance with my invention, a petroleum oil distillate or residuumis extracted with an aromatic nitro-compound, for example, nitrobenzene,whereupon there is produced a highly refined oil substantially all ofwhich is of a saturated compound character, and which contains the moststable constituents of the distillate or residuum. Further, inaccordance with this invention, the oil produced is of good stabilityand may be of higher viscosity than white mineral oils heretofore foundon the market.

It desirable that a white mineral oil should comprise for the most part,saturated hydrocarbons, particularly hydrocarbons of those series inwhich the hydrogen to carbon ratio is high. It is generally recognizedthat petroleum oil is essentially a mixture of hydrocarbons of variousgroups or homologous series of compounds, such for example as theparafiins of general formula CnH2n+2, the olefines, whose generalformula is CnHB-n, the hydro-aromatics and the polymethylenes of thesame empirical formula. and various other series of hydrocarbons inwhich the hydrogen to carbon ratio is less than in these compounds justmentioned. some of which may be of a chain structure and others of aring structure. A large number of individual compounds of each seriesand of different boiling points are present in petroleum oil. 7

The various types of crude petroleiun which are generally classifiedinto the three groups, namely, paraffine base, naphthenic or asphaltbase, and mixed base, contain the various series of hydrocarbonsheretofore mentioned, in different proportions. For example, in theparaffine base crudes, such as those produced in the oil fields ofPennsylvania. there is a relatively high proportion of hydrocarbonshaving a chain structure and a high hydrogen to carbon ratio, whereas inthe so-called naphthenic or asphalt base crudes there is a relativelylarge proportion of hydrocarbons having ring structures, and a lowhydrogen to carbon ratio. The mixed base crudes such as are obtainedfrom the Mid-Continent oil fields contain hydro-carbons in proportionsintermediate these two extremes.

White mineral oils produced, in accordance with my process, are preparedfrom suitable fractions of a crude petroleum, and in particular,fractions which heretofore have not been used in the preparation ofwhite mineral oils or oils of a similar character. For example, a heavydistillate from a mixed base crude from the Mid-Continent area may beused in the preparation of a white mineral oil in accordance with myprocess. It is not however my intention to be limited to a product madefrom any specific crude or fraction of a crude, but to include withinthe scope of this invention a product characterized by certain desirableproperties hereinafter described, prepared from any crude petroleum orfraction thereof which it is found desirable to use for such purposes,as well as the particular process for preparing such product, as isherein set forth.

As before stated, the various types of crude petroleum and theirfractions differ from one another in the proportion of the variousseries of hydrocarbons which each contains. This is evidenced by thephysical properties of the various oils and particularly by therelationship of the specific gravity to the viscosity of one oil ascompared with another. For example, oil from a Pennsylvania crude with aviscosity of 400 seconds Saybolt Universal at 100 R, will show aspecific gravity at F. of about 0.878, whereas an oil of correspondingviscosity produced from a naphthenic crude, as one from the Gulf Coastarea, will show a specific gravity of about 0.933 at 60 F. Therelationship between the viscosity and gravity indicates the degree ofthe paraflinic or naphthenic character of the oil.

If a given crude petroleum be distilled into successive fractions andthe specific gravities and viscosities of the several fractionsdetermined, it will be found that they conform to the generalrelationship 10 log(V 38) in which G is the specific gravity at 60 F., Vis Saybolt Universal viscosity at 100 F., and a is a constant knownasthe viscosity-gravity constant. Fractions from each of the differenttypes of crudes have different viscosity-gravity constants. Suchconstants are lower for fractions of the paraflinic crudes than are theconstants for fractions of the naphthenic crudes. This necessarilyfollows from the relation of the constants of the crudes themselves,since such constants are different for different crudes, and

, the paraflinic crudes have lower viscosity-gravity constants than dothe naphthenic crudes. a ticle entitled The Viscosity-Gravity Constant fPetroleum Lubricating Oils", by J. B. Hill and B. Coats which will befound in volume 20,

page f64l et seq., Industrial and Engineering Chemistry for June, 1928,explains the determi- I nation ofthe constant for several typical oils.

'Ifheviscosity-gravity constant is, therefore, an

' find ex of the paraffinicness or naphthenicness of Yfanf oil 'sinceregardless of the fraction upon whichjthe specific gravity and theviscosity are tali'n. when the particular specific gravity and 7viscosity are substituted in the formula and the viscosity-gravityconstant determined, the constant will.be substantially the same for anygiven crude.

The viscosity-gravity constants for some of the I have found that thewhite oils produced by my process .are much more paraffinic than whiteoils which have heretofore been commercially produced. For example, theoils produced by my process may have a viscosity-gravity constant of0.795, whereas the ordinary white min-.

eral oils have viscosity-gravity constants ranging from about 0.800 toabout 0.840. White oils of high viscosities, for example of 100 secondsSaybolt Universal at 100 F. or above, which have been known heretofore,have viscosity-gravity constants greater than 0.8030. None of the whitemineral oils heretofore known have viscosity-gravity constants as low asviscositygravity constants of oils of corresponding viscosities whichmay be produced by my process.

In accordance with my invention, the process of which Ihave set forth inits broadest aspect in my copending application Serial No. 206,388,filed on July 6, 1927, which issued into U. S. Patent No. 1,788,569 onJan. 13,1931, the oil fraction to be treated is agitated withnitrobenzene. The mixture is allowed to separate into layers, one ofwhich contains substantially all of the nitrobenzene and that portion ofthe oil which dissolved therein, the other layer comprising that portionof the oil which did not dissolve in the nitrobenzene. This lastmentioned layer may be subjected to a further treatment withnitrobenzene in case it is desired to remove additional quantities ofconstituents soluble in the aforesaid solvent, which remain in the oilafter the first extraction.

When the extraction with nitrobenzene is completed, separation from thesolvent of that portion of the oil which dissolved therein is effected,as for example, by distillation, whereupon the extract results as aby-product and may be used in the manufacture of cable oil s,lubricating oils or the like. The oil which remains insoluble in thenitrobenzene, that is, that portion which is to be further treated toform the desired final product, is subjected to a light acid treatmentto further remove objectionable compounds, which if allowed to remain inthe oil might cause discoloration of the oil. Due to the fact that mostof the undesirable constituents of the oil have by the nitro-benzeneextraction already been removed, only a small amount of acid is requiredto produce a finished product.

It is to be understood that when circumstances warrant, as for example,in the treatment of a highly viscous oil, the nitrobenzene extractionmay be carried out at elevated temperatures in order to effect acomplete solution of the oil therein so that all portions of the oil maybe brought into intimate contact with the nitrobenzene and ahomogenousliquid solution formed. After such treatment the mixture is cooledwhereupon it separates into two layers, the upper being a solution ofnitrobenzene in the more paraflinic portion of the oil, and the lower asolution of the more naphthenic portion of the oil in nitrobenzene.

However,.in lieu of this heating, I may simply agitate the cold mixture.

.Before removing the nitrobenzene from the upper layer of paraflinic oilobtained by the pro-. cedure just described, extraction of furthernaphthenic bodies from the paraflinic portion of the oil maybe efiectedby adding a further quantity of nitrobenzene, allowing layers to formand separating the layers. Such extraction may be repeated two or threetimes, or as often as desired. In the manufacture of a white mineral oilin accordance herewith, it is preferable to use a dewaxed oil as thestarting material. Such oil, for example, may be a high viscosityfraction from a Mid-Continent crude from which the wax has been removedby any of the well-known processes. It is not to be understood, however,that this process is to be limited to a dewaxed oil, since it may,

be used in the treatment of oil fractions containing large amounts ofsolid hydrocarbons, in which instance such hydrocarbons may be removed'or partially removed after the oilhas been extracted with.nitrobenzene.

As an example ofmy process, but which is not to be considered aslimiting my invention, a dewaxed distillate from a Mid-Continent crude,having a viscosity of 118 seconds Saybolt Universal at 210 F., and aspecific gravity of 0.9200, is treated with nitrobenzene in theproportions of about one part of oil to about two parts of nitrobenzeneby weight. After agitating, the mixture is allowed to settle and theportion of the oil which remains insoluble in the solvent is separated.Another portion of nitrozenzene in about the proportions used in thefirst extraction is added to the oil so removed, and the operation isrepeated. In this manner four extractions with nitrobenzene are carriedout. 1

The nitrobenzene soluble portion of the oil which amounts to about 65%of the original oil fraction is separated from the nitrobenzene bydistillation, whereupon it is suitable for use, either alone or blended,in the manufacture of such valuable products as cable oils, lubricatingoils or the like.

The portion of the oil fraction which remains undissolved in thenitrobenzene after the several extractions have been completed isseparated by distillation from any nitrobenzene which remains admixedtherewith. This insoluble portion represents about 35% by volume of theamount of the original fraction at the beginning of the process.

The nitrobenzene insoluble portion of the oil is treated with two poundsper gallon of 663B. sulphuric acid to eflect further purificationthereof, whereupon the acid treatment removes the small amount ofundesirable constituents still remaining in the oil after thenitrobenzene extraction. The acid sludge which forms is removed from theoil and the oilis treated with an adsorbent ,agentras fullers earth, toproduce a water-white product.

The final product obtained by such treatment as has been described indetail, is an oil having a viscosity of 1031 seconds Saybolt Universalat 100 F., a specific gravity of 0.8805 at F., and a viscosity gravityconstant of 0.797. I

While in the above example I have stated that nitrobenzene may be usedas the solvent, I do not intend to limit my invention to this particularcompound. It is to be understood that other solvents such asnitrotoluene, mono-nitronaphthalene or the like, or a mixture of themmay be used and come within the scope of solvents contemplated by myinvention.

An advantage of my process, in addition to those heretofore mentioned,is that the amount of the oil fraction which is converted into acidsludge is very small as compared with the amount incident to the drastictreatments used in prior processes for the manufacture of white mineraloils. In the example given above, from a total of 100 parts of thefraction treated there were obtained parts of an oil of higher valuethan the general run of lubricating oils, and 32.7 parts of the finaldesired white mineral oil product,

leaving a loss of only 2.3 parts in the form of acid sludge. Thiscompares with a loss of about 50% of the amount of the original oilfraction which "forms acid sludge when prior processes are used in thepreparation of such oils. In my process this loss is low in spite of thefact that I am able to use a fraction whose viscosity is much higherthan the viscosity of those oils customarily used in the preparation ofwhite mineral oils. If the oils of high viscosity which I am able to usewere used in the prior processes, a loss in the form of acid sludge muchgreater than 50% might be expected, provided, of course, that suchhigher viscosity fractions could be acid treated by such. prior processto an extent to produce a white mineral oil. The low treating lossincident to my process can be explained by the removal by thenitrobenzene of the chemically unstable compounds which normally react.withthe acid to form sludge. In my process, instead of large quantitiesof acid sludge being produced, practically all of the oil treated isconverted into products of high marketable value.

Another advantage of producing a white mineral oil in the mannerdescribed is that the amount of sulphuric acid required is low comparedwith the amount of sulphuric acid required, or which would be requiredin the treatment of the high viscosity oils for which my process isparticularly adapted, by methods for producing white mineral oils inaccordance with prior practice. In producing the usual medicinal oilshaving viscosities of from around 100 to 300 seconds Saybolt Universalat 100 F., the fuming sulphuric acid required is of the order of 75% byweight of the oil treated. -As indicated by the above example, in myprocess, treatment with only about 25% of 66 B. sulphuric acid wasnecessary to produce a white medicinal oil of 1031 secondsSayboltUniversal at 100 F. To produce a water-white oil of thisviscosity by straight acid treatment, assuming that such treatment couldbe accomplished satisfactorily would require a considerably greaterquantity of acid.

It is to be noted that in the treatment of an oil in accordance with myinvention, an oil of comparatively high value results as a by-product,whereas, in the sulphuric acid processes only acid sludge results, whicheven if recovered, is of little value.

It has long been recognized that the higher the viscosity of a medicinaloil, the more valuable it is, and as my process produces white mineraloil of higher viscosity than it has been possible heretofore to produce,both the process and the product represent a distinct and decidedadvance in the art.

It is to be understood that this process, in addition to beingparticularly adaptable for use in the preparation of white mineral oilsto be used for medicinal purposes, is also suitable for I f I 4 thepreparation of oils such as those commonly known as technical whiteoils, which are used in" various industries, as for example, ;the bakingindustry. v 1

In-the appended claims, the term white mineral oil is used-to includemedicinal oils, technical white oils and other highly refined viscousoils jao of a" like character, the term "nitrobenzene 's employed in agenericsense to include that material and equivalent. aromatic nitro.compounds or mixtures thereof, and the term viscous oil comprehends oilof substantial viscosity, i. e., having a viscosity of the order of 50seconds Saybolt Universal at F., and up-.-

wards.

What I claim is:

1. In the art of preparing a white mineral oil,

the step which comprises extracting a viscous mineral oil distillatecontaining paraifinic and naphthenic hydrocarbons with nitrobenzenethereby to remove from the distillate substantial amounts of itsnaphthenic hydrocarbon content. 2. In the art of preparing a whitemineral oil, the step which comprises repeatedly extracting a viscousmineral oil distillate containing paraffinic and naphthenic hydrocarbonswith nitrobenzene, thereby to remove from the distillate substantialamounts ofits naphthenic hydrocarbon content. l

. 3. In the art of preparing a whiteamineral oil having a viscosity-gravity constant not higher than 0.795, the step which comprisesextracting a viscous mineral oil distillate containing paraffinic andnaphthenic hydrocarbons with nitrobenzene, thereby to remove from thedistillate substantial amounts of its naphthenic hydrocarbon content.

4. In ,the art of preparing a white mineral oil having a viscosityof atleast 500 seconds Saying the nitrobenzene from that portion of the oilwhich remains undissolved therein and treating the undissolved portionof oil with sulphuric acid.

6. In the art of preparing a white mineral oil, the process whichcomprises repeatedly adding nitrobenzene to a viscous mineral oil andagitating the mixture, separating the nitrobenzene from that portion ofthe oil which remains undissolved therein thereby to dissolve from the.oil a substantial part ofthe components thereof which react withsulphuric acid and treating the undissolved portion of the oil withsulphuric acid.

7. In the art of preparinga white mineral oil the process whichcomprises extracting a viscous mineral oil distillate with nitrobenzeneto dissolve from the oil a substantial part of the components thereofwhich react 'with sulphuric acid,

separating the nitrobenzene from that portion of the distillate whichremains undissolved there in, treatingthe undissolved portion with afur- 'ther quantity of nitrobenzene, and again separating thenitrobenzene to further dissolve from the oil components thereof whichreact with sulphuric acidtherefrom, treating the undissolved oil withsulphuric acid, separating the acid sludge,

from the oil, and treating the oil with an adsorbent agent.

8; In the art of preparing a white mineraloil the process whichcomprises repeatedly extracting a viscous mineral oil distillate withnitrobenzene to dissolve from the oil a substantial part of thecomponents thereof which react with sulphuric acid, separating thenitrobenzene from the portion of the oil which remains undissolvedtherein, treating the undissolved portion of oil with sulphuric acid,separating the acid sludge from the oil, adding fullers earth to thetreated oil, and filtering the oil.

9. A white mineral oil having a viscosity between 500 seconds SayboltUniversal at 100 F. and 1031 seconds Saybolt Universal at 100 F.

10. A white mineral oil having a viscosity-gravity constant not higherthan 0.797 and a viscosity between 500 seconds Saybolt Universal at 100F. and 1031 secondsSaybolt Universal at 100 F.

11. A white mineral oil having a viscosity 'greatefthan 100 secondsSaybolt Universal'at 100 F. and viscosity-gravity constant not higherthan 0.8030. v

12. A white mineral oil having a viscosity of at least 500 secondsSaybolt Universal at 100 F. and a viscosity-gravity constant not higherthan 0.8030. g

I 13. In the art of refining mineral oils, the process which comprisesextracting a viscous mineral oil distillate with nitrobenzene todissolve from' the oil a substantial part of the components thereofwhich react with sulphuric acid, separating the; nitrobenzeneirom thatportion of the distillate which remains undissolved therein.

treating the undissolved portion with a further quantity of nitrobenzeneto further dissolve from the oil components thereof which react withsulphuric acid, and again separating the "nitrobenzene therefrom,treating the undissolved oil with "substantial part of the componentsthereof which react with sulphuric acid, separating the nitrobenzenefrom that portion of the 'oil which remains undissolved-therein andtreating the 'undissolved portion of oil with sulphuric acid.

16. In the art of refining mineral oils, the process which comprisesrepeatedly adding nitrobenzone to a viscous mineral oil and agitatingthe mixture, separating the nitrobenzene from that portion of the oilwhich remains undissolved the-rein, thereby to dissolve from the oil asubstantial part of the components thereof which react with sulphuricacid, and treating themdissolved portion of the oil with sulphuric acid.

17. In theart of refining mineral oils, the process which comprisesrepeatedly extracting a viscous mineral oil distillate with nitrobenzeneto. dissolve from the'oil a substantial part of the componentsthereof'which react with sulphuric acid, separating the nitrobenzenefrom the portion of the ofl which remains undissolved thereoil asubstantial part of the components thereof which will react with asludge forming agent,

separating the nitrobenzene trom the portion of the oil which remainsundissolved therein, and

treating theundissolved portion 01' the oil with a sludge forming agent.1 L

n SEYMOUR W. FERRIS..

